Keys have been used to unlock automobile doors or start up an automobile engine. However, when a key is used for such purposes, a malicious person other than an automobile owner might drive an automobile, for instance, by stealing the key or by picking a lock.
Under the above circumstances, a security enhancement method is disclosed, for instance, by JP-A-61-53972 and JP-A-6-72291. This method provides enhanced security by using a fingerprint, which is biometric feature information, as means of personal identification instead of a key for automobile door unlocking and engine startup.
However, fingerprints can be forged. Therefore, another security enhancement method is disclosed, for instance, by JP-A-2001-184507 and JP-A-2003-30632. This method provides enhanced security by using an image containing a finger's blood vessel pattern, which differs from one person to another, as biometric feature information. This method radiates a finger with a light source containing an infrared or near-infrared light component (hereinafter referred to as an infrared light source). The infrared or near-infrared light is then transmitted through the finger and radiated from the finger. The intensity distribution of the resulting infrared or near-infrared radiation contains the information about a blood vessel pattern (mainly a vein pattern) of the finger. This blood vessel pattern is detected by image pickup means and compared with a preregistered blood vessel pattern to judge whether they match. When they match, personal authentication is achieved because it is concluded that the detected blood vessel pattern belongs to a person having the blood vessel pattern which was pre-registered.
Further, a device similar to a personal identification device that provides personal authentication by using a finger's blood vessel pattern as biometric feature information is disclosed, for instance, by JP-A-10-127609. This device uses an infrared light source to radiate a living body with infrared light, picks up the resulting light reflection with image pickup means, and uses an image containing a blood vessel pattern.
Patent Document 1: JP-A-61-53972
Patent Document 2: JP-A-6-72291
Patent Document 3: JP-A-2001-184507
Patent Document 4: JP-A-2003-30632
Patent Document 5: JP-A-10-127609